Abstract / Description of output
The aim of the present study was to test the hypothesis that differences in function and expression of cannabinoid (CB1) and vanilloid (VR1) receptors exist between sensory nerves innervating arteries and veins. Anandamide (288 - 1275 nmoles) produced a dose-dependent fall in blood pressure and an increase in ventilation when injected via i.a. and i.v. routes in anaesthetised rats. The CB1 antagonist SR141716 (1mg kg-1) blocked the cardiorespiratory response to i.v., but not i.a., anandamide. The VR1 antagonist capsazepine (1 mg kg-1) significantly attenuated cardiorespiratory responses evoked by both i.a. and i.v. anandamide. Doses of SR141716 (0.03 mg kg-1) and capsazepine (0.3 mg kg-1) that, when administered alone, had no effect on anandamide-induced responses, were able to abolish responses when coadministered. Immunolabelling of perivascular nerves revealed that CB1 receptors and VR1 receptors had a similar distribution in arteries and veins. We conclude from these results that both CB1 and VR1 receptors on perivascular nerves contribute to the cardiorespiratory responses of i.v. administered anandamide, whereas responses to the i.a. route are predominantly VR1-mediated. These differences are not due to differences in receptor expression on sensory nerves innervating arteries and veins. It would appear there is a synergistic interaction between CB1 and VR1 receptors following i.v. injection of anandamide.
Keywords / Materials (for Non-textual outputs)